Hannibal Lecktor: If one does what God does enough times, one will become as God is.
Hannibal Lecktor: Have you ever seen blood in the moonlight, Will? It appears quite black.
Will Graham: I thought you might be curious to see if you're smarter than the person I'm looking for.
Hannibal Lecktor: Then, by implication, you think you're smarter than me, since it was you who caught me.
Will Graham: No. I know that I'm not smarter than you.
Hannibal Lecktor: Then how did you catch me?
Will Graham: You had disadvantages.
Hannibal Lecktor: What disadvantages?
Will Graham: You're insane.
Chosen answer: He figured out from evidence at one of the crime scenes that the Tooth Fairy drives a van. Graham noticed that at one of the houses, the Tooth Fairy knew everything he had to do and bring with him and at the other house, he didn't know about the new lock on the door. He concludes that this is because the Tooth Fairy got his information from the same home movies that Graham was watching. Once the films were traced to the lab where Dolarhyde worked, it was easy to link them back to him as the only person who'd had access to both families' videos and also drove a van.
Captain Defenestrator